It's rare these days - especially as the referendum debate rages with both sides to varying degrees struggling to tell the public the truth, the whole truth, and absolutely nothing but the truth - that political figures are willing to say exactly what they think in public.

But the union movement, in the recently elected boss of the GMB, Tim Roache, might just have found themselves someone who might.

He's worked for the union for decades, starting as a teenager in the post room. But after years of working his way up, now he's in charge, Roache is clearly determined to change things.

And in an interview with me for Radio 4's World at One programme, he didn't hold back.

A few days before his first union congress as leader, to use his phrase, he thinks unions must "freshen up" - he wants to make his union, and perhaps the whole movement, more relevant to his members and politics in a wider sense.

'Half-hearted Remain'

First things first, like many others in the Labour movement, he is worried the referendum could be lost because Labour voters simply stay at home - he describes himself as an "angry Remain", and the debate so far, as a "Tory bunfight", when it actually, he says matters hugely to workers and workers rights.

And although he supported Jeremy Corbyn for the leadership, he believes he is only a "half-hearted Remain", and urges him to take a more prominent position in the campaign.

What's more striking perhaps is Roache's obvious wider concern about the Labour Party. I ask if Labour is in the kind of shape it needs to be to win the next general election - "absolutely not", comes the answer, it has "failed to get its message across", he says.

Image copyrightGMBImage caption
Tim Roache won the GMB leadership contest with 56.7% of the vote

Clearly, Roache believes the party's performance is not yet good enough and it has to improve.

After May's local elections, the GMB leader had warned that the party ought to have won many more seats. But as a Corbyn backer, and with anxieties across the Labour party about the leadership's approach to the referendum, this message can't be dismissed as the party's usual suspects going after him.

And Roache has an equally tough message for MPs who have groused about Mr Corbyn's leadership, warning that the party has been "tearing itself apart" and they have a responsibility to get behind the leader with his huge mandate from the membership.

Union voices matter - they don't just provide the Labour Party with much of its cash, but much of its power on the ground.

And on Trident, on how he wants unions to look different, whether Jeremy Corbyn should shave off his beard, he has plenty more to say. You can listen to my full interview with him on the World at One from 13:00 BST.